With the increasingly extensive use of network technologies, a great variety of networking devices have been developed to suit user needs. For example, one who needs frequent use of broadband services may require an Asymmetric Digital Subscriber Line (ADSL) modem coupled to a central office (CO) line or a cable modem coupled to a TV signal cable in order to make Internet connection. As wireless network technologies gradually mature, cable-based broadband Internet connection has given way to the wireless version by degrees, not only because the latter can be implemented with far less cables than required in the former, but also because one who has made such wireless connection through an electronic device is allowed to move about freely. However, despite the huge convenience it brings to network applications, wireless broadband Internet connection has such drawbacks as low data security and high susceptibility to interruption. To overcome these drawbacks while maintaining the advantage of not requiring additional network cables, the power line communication (PLC) technology was devised and is now available for use. Generally speaking, a power line networking device is advantageous over modems and like networking devices in that it does not require extra cabling, provides wide network coverage, allows easy connection, and has high data rate. In fact, a power line networking device relies on no more than a household power line to make broadband Internet connection. Therefore, a client end only has to plug a power line networking device into a wall socket, and broadband Internet connection can be established directly through the power line; in other words, there is no need for a broadband network service provider to install additional wires at the client end.
As its name suggests, power line communication uses existing power lines in a building to transmit network signals. In order to apply PLC technology, PLC devices (e.g., network bridges) are required, which are connected to power line sockets at different locations to convert network signals and thereby enable transmission of network signals via power lines. Now that power lines are essential to each building, using power lines as the backbone medium for network transmission not only spares the trouble of cable distribution, but also reduces the cost and time of installation. Also, the integrity of the interior design of a building need not be compromised. In a nutshell, PLC is an ideal solution to the aforesaid problems. However, as a power line is designed solely as a power-supplying medium in the first place and is not configured for high-quality signal transmission, the voltage carried by a power line will fluctuate with the load of the electronic device being powered or even generate electromagnetic radiation. The electronic device being powered may also generate noise. All the foregoing interferes with network signals. A minor interference can lower the quality of network signal transmission; a significant interference, on the other hand, can damage network signals completely. One solution to the noise interference problem is to install a filter in a PLC device, so as for the filter to filter out noise in the power line. Nevertheless, since not all electronic devices generate a high level of noise, one who has bought a PLC device equipped with a filter can never know if the filter provides the expected filtering effect, or which electronic device should the PLC device be connected to in order to filter out the strongest source of noise.
To effectively solve the problems stated above, the inventor of the present invention developed a PLC device switchable between noise detecting and filtering functions. This PLC device, as shown in FIG. 1, not only can effectively detect noise generated by various electronic devices, but also can filter out the noise detected, thereby increasing the quality of a network environment. Referring to FIG. 1, the PLC device 1 includes a power receiving port 11, a filtering unit 12, a power output port 13, a switching unit 14, and a processing unit 15. The power receiving port 11 has one end connected to a power supply unit 10 in order to receive a power signal transmitted from the power supply unit 10 and a network signal carried by the power signal. The filtering unit 12 has a first end connected to the opposite end of the power receiving port 11. The switching unit 14 includes a first connecting end A1, a second connecting end A2, and a control end A0. The first connecting end A1 is connected to the first end of the filtering unit 12, the second connecting end A2 is connected to a second end of the filtering unit 12, and the control end A0 is switchable into conduction with only the first connecting end A1 or only the second connecting end A2. The power output port 13 has one end connected to the control end A0 and the opposite end connected to a load L. The processing unit 15 is connected to the first end of the filtering unit 12 and includes a bridge module 151, a detection module 152, and a display module 153. Once the control end A0 is switched into conduction with the first connecting end A1, the bridge module 151 receives the network signal transmitted from the power receiving port 11. Once the control end A0 of the switching unit 14 is switched into conduction with the second connecting end A2 instead, the filtering unit 12 can filter out the noise generated in the power signal by the load L.
More specifically, in the state in which the control end A0 has been switched into conduction with the first connecting end A1, both the power output port 13 and the processing unit 15 are connected to the first end of the filtering unit 12 such that the filtering unit 12 is unable to filter out the noise generated by the load L. The detection module 152 in this state receives the power signal from the load end, detects the level of the noise generated in the power signal by the load L, and shows the current noise level. Conversely, in the state in which the control end A0 of the switching unit 14 has been switched into conduction with the second connecting end A2, the power output port 13 and the processing unit 15 are connected via the filtering unit 12, thus allowing the filtering unit 12 to filter out the noise generated in the power signal by the load L. Therefore, after receiving the power signal transmitted from the power receiving port 11, the bridge module 151 can correctly obtain, by conversion, the network signal carried by the power signal and then delivers the network signal to an external network apparatus either through a physical connecting line or wirelessly. When it is desired to lay out a power line network in a place where there are a plurality of electronic apparatuses, the control end A0 of the switching unit 14 can be switched into connection with the second connecting end A2, and then the PLC device 1 is sequentially connected to each electronic apparatus. By doing so, the level of the noise generated by each electronic apparatus during operation can be known. The PLC device 1 is eventually applied to the electronic apparatus generating the highest level of noise, with the control end A0 switched into connection with the first connecting end A1 in order to filter out the strongest source of noise in that place.
The PLC device 1 described above can effectively enhance noise filtering, thus greatly increasing the practical value of the conventional PLC devices in general. However, as the PLC device 1 is so designed as to allow passage of the power signal and the network signal (and the noise generated in the power signal by the load L), the switching unit 14 must be a high current resistant element if the path of the power signal and the network signal is controlled solely by the switching unit 14; otherwise, the switching unit 14 cannot withstand the high current of the power signal. Generally speaking, high current resistant elements are both costly and bulky. Using a high current resistant element as the switching unit 14 not only raises the production cost of the PLC device 1, but also hinders product miniaturization.
Hence, while the inventor of the present invention has devised a practical PLC device featuring excellent performance in application, the spirit of constant pursuit of perfection has driven the inventor to make further efforts and improve the existing design from the perspective of production. The issue to be addressed by the present invention is to bring about PLC device optimization and enable the foregoing PLC device 1 to use a low current resistant element as the switching unit 14, thereby effectively downsize the finished product and greatly reduce production cost.